The present invention relates to a method and apparatus for controlling the operation, and in particular the current flow, of an electromagnetic load such as a fuel injection valve.
It is conventional to apply a high-amperage current to injection valves at the beginning of a trigger pulse, and to maintain the high-amperage current until the injection valve has opened at which time the control current reaches a lower and substantially constant value. Once the fuel injection solenoid valve is opened, no other mechanical work needs to be performed, and therefore a smaller current is sufficient for maintaining the open position of the valve than is required for opening the valve itself.
In the conventional valve control system, a series connection of load and current measuring device is connected directly in parallel to an energy source until the solenoid valve has been securely attracted. Only thereafter is the valve current reduced to the level of a holding current and maintained at the same value until the end of the excitation signal trigger pulse. Also, a corresponding device has been known wherein the subsequent holding current is timed, i.e., the current supply to the load is cut in-and-out in dependence on the current. With the aid of this device, a reduction in power consumption can be achieved at least during the holding phase.
It has now been found that the timing of the current supply during the holding phase alone does not as yet represent an optimum condition insofar as energy consumption of an injection valve is concerned. Although the requirements regarding a maximally timed opening and closing of the valve are satisfactorily met.